1. Field of the Invention
The present invention relates to an image display apparatus and a manufacturing method thereof.
2. Related Background Art
An image display apparatus using electrons requires an envelope unit for keeping a vacuum atmosphere, an electron source for emitting the electrons, a drive circuit thereof, an image forming member including a fluorescent material that emits the light upon impingement of electrons, an acceleration electrode for accelerating the electrons toward the image forming member, and a power source thereof. Further, in an image forming apparatus employing a flat envelope unit as in the case of a thin type image forming apparatus, there might be a case where support columns are used as an atmospheric pressure resistant structured body.
Two types of electron emission elements such as a hot-cathode element and a cold-cathode element have hitherto known as the aforementioned electron emission elements. What is known as the cold-cathode element of these two types may be, for instance, a field emission type element (which will hereinafter be abbreviated to FE type), a metal/insulation layer/metal type emission element (which will hereinafter be abbreviated to MIM type) and a surface conduction type emission element.
FIG. 7 is a perspective view showing one example of a display panel unit configuring a flat type image forming apparatus, wherein a part of the panel is cut off in order to have its internal structure viewed.
Referring to FIG. 7, there are illustrated a rear plate designated by the numeral 3115, an external frame 3116 and a face plate 3117. The rear plate 3115, the external frame 3116 and the face plate 3117 configure an envelope unit (a hermetic container) for keeping an interior of the display panel in vacuum. A substrate 3111 is fixed to the rear plate 3115. (N×M) pieces of cold-cathode elements 3112 are formed on this substrate 3111 (N and M are positive integers of 2 or larger and are properly set corresponding to a desired number of pixels). Further, the (N×M) pieces of cold-cathode elements 3112 are, as shown in FIG. 7, wired by M-pieces of line-directional wires 3113 and N-pieces of row-directional wires 3114. A unit constructed of the substrate 3111, the cold-cathode elements 3112, the lie-directional wires 3113 and the row-directional wires 3114, is called a multi electron beam source. Moreover, an insulating layer (not shown is formed between these two types of wires leastwise at an intersection between the line-directional wire 3113 and the row-directional wire 3114, whereby the electric insulation is kept. A fluorescent screen 3118 composed of fluorescent materials is formed on the underside of the face plate 3117, and phosphors (not shown) in three primary colors such as red (R), green (G) and blue (B) are separately coated thereon. Further, black substances (not shown) are provided between the respective color fluorescent materials configuring the fluorescent screen 3118, and a metal-backed member 3119 composed of Al, etc. is formed on the surface, on the side of the rear plate 3115, of the fluorescent screen 3118.
The symbols Dx1 to Dxm, Dy1 to Dyn and Hv represent hermetically-structured electric connection terminals provided for electrically connecting the display panel described above to an electric circuit (not shown). The terminals Dx1 to Dxm electrically connect to the line-directional wires 3113 of the multi electron beam source, the terminals Dy1 to Dyn electrically connect to the row-directional wires 3114 of the multi electron beam source, and the terminal Hv to the metal-backed member 3119, respectively.
Further, an interior of the hermetic container is kept in vacuum on the order of 10-6 Torr. A means for preventing the rear plate 3115 and the face plate 3117 from being deformed or broken die to a pressure difference between the interior of the hermetic container and the exterior, is needed as a display areal size of the image display apparatus increases. A method based on thickening the rear plate 3115 and the face plate 3117 causes an increase in weight of the image display apparatus and also an image distortion and a parallax when viewed in an oblique direction. By contrast, referring to FIG. 7, there is provided a structure sustaining member (which is known as a spacer or a rib) 3120, constructed of a comparatively thin glass plate, for sustaining the atmospheric pressure. Thus, the substrate 3111 formed with the multi electron beam source and the face plate 3117 formed with the fluorescent screen 3118, are spaced normally sub-millimeters through several millimeters, and, as described above, the interior of the hermetic container is kept in high vacuum.
In the image display apparatus employing the display panel explained above, when a voltage is applied to the respective cold-cathode elements 3112, via the off-container terminals Dx1 to Dxm and Dy1 to Dyn, electrons are emitted from the respective cold-cathode elements 3112. Simultaneously, a voltage as high as several hundreds of volts (V) through several kilovolts (kV) is applied to the metal-backed member 3119 via the off-container terminal Hv, and the emitted electrons are accelerated and thus made to impinge on the internal surface of the face plate 3117. The color fluorescent materials configuring the fluorescent screen 3118 are thereby excited and become luminous, thus displaying an image.
Without being limited to the image display apparatus utilizing the electron emitting elements, there are known an image display apparatus employing electroluminescence elements and an image display apparatus known as a plasma display. Any type of image display apparatus includes an envelope unit that accommodates the display elements inside.
It is effective that a low melting point metal, etc. is used as a connecting member (serving for at least one of bonding and a hermetic connection) for connecting the substrate and the external frame which structures this envelope unit.